1. Technical Field
The present invention relates to a method of alignment between sheet materials, which is suitably used for alignment, for example between a liquid crystal display cell and a lenticular lens, which constitute a liquid crystal display panel, a method of alignment, a substrate assembling method and an aligning apparatus.
2. Prior Art
There has been a remarkable progress in the popularization of a liquid crystal display device as an image display device used for a monitor of a personal computer and various other monitors. The liquid crystal display of this type is generally constructed in such a manner that a backlight as a sheet light source for illumination is disposed on the backside of a display panel, a liquid crystal surface having a given extent is illuminated to have uniform brightness as a whole, and thus an image formed on the liquid crystal display surface of the display panel can be visible.
The conventionally used display panel includes signal and gate lines, a TFT having an amorphous silicon layer or the like formed thereon, a color filter, and so on, all of which are laminated between two glass substrates. In such a display panel, a light emitted from the backlight is dispersed into three colors of R (Red), G(Green) and B (Blue) by the color filter to form a pixel of each of R, G and B colors.
Especially, in a projection type liquid crystal display device, the quantity of transmitted lights is increased by condensing incident lights using the lenticular lens and converging the lights to the opening portion of the pixel. The example thereof is described in Japanese Patent Laid-Open No. Hei 3-244286.
In recent years, as a technology for removing filters from the display panel, the display panel using the lenticular lens has been developed.
FIG. 12 schematically shows the structure of such a display panel using the lenticular lens. In FIG. 12, a reference numeral 1 denotes a liquid crystal display cell; and 2 a lenticular lens.
The liquid crystal display cell 1 includes a liquid crystal sealed in between two glass substrates 3A and 3B, a signal line 4s, a gate line (not shown), a TFT device, a display electrode, and so on. In the glass substrate 3A, a black matrix 5 is formed to cover the signal line 4s and the gate line.
The lenticular lens 2 includes a number of arrayed condenser lens portions 7 formed to be roughly circular-arc in section. As shown in FIGS. 12 and 13, the roughly circular-arc section of each of the condenser lens portions 7 is formed to be continuous in the extended direction of the signal line 4s. Each condenser lens portion 7 is formed such that in the width direction thereof, totally three opening portions 8 can be positioned between joints 7a and 7a of the other condenser lens portions 7 arrayed in both sides thereof, each opening portion 8 being defined by a black matrix 5 and forming one pixel.
In such a display panel having the lenticular lens 2, a light emitted from the backlight unit (not shown) as a light source is dispersed into three colors of R, G and B by a diffraction grating provided in the backlight unit, and the dispersed lights are made incident on the lenticular lens 2. In this case, the incident angles of the dispersed lights are different from one another for each color, and each dispersed light is parallel rays of light. Thus, the light of each color condensed at the condenser lens portion 7 of the lenticular lens 2 forms an image at each of the three opening portions 8 arrayed between the joints 7a and 7a. As a result, the pixels of three colors, R, G and B are formed side by side in the width direction of each condenser lens portion 7.
In the manufacturing process of such a display panel, in order to accurately align the position of each color image (light) formed by the light condensed at the condenser lens portion 7 of the lenticular lens 2 with the position of each opening portion 8 formed in the glass substrate 3A, alignment must be performed between the lenticular lens 2 and the liquid crystal display cell 1.
For the purpose of performing alignment between the lenticular lens 2 and the liquid crystal display cell 1, technologies have already been disclosed in Japanese Patent Laid-Open No. Hei 8-211515 and Japanese Patent Laid-Open No. Hei 9-113215. According to the technology disclosed in Japanese Patent Laid-Open No. Hei 8-211515, a mark for alignment is formed in the lenticular lens 2 or a substrate of the opposite side thereof (liquid crystal display cell 1), and alignment is performed by using this mark. According to Japanese Patent Laid-Open No. Hei 9-113215, a xe2x80x9cplanar areaxe2x80x9d not roughly circular-arc in section is formed in the lenticular lens 2, and alignment is performed by viewing this planar area through a microscope.
However, in the foregoing conventional technologies, the mark for alignment must be provided in the lenticular lens 2 or the substrate, and the planar area must be formed in the lenticular lens 2. Thus, extra time and labor for forming such a mark or a planar area were necessary.
In its manufacturing process, the lenticular lens 2 is cut out in a specified size from a web continuous in the extended direction of the condenser lens portion 7 roughly circular-arc in section. At this time, the mark for alignment or the planar area is formed in this web manufacturing stage. If the mark for alignment or the planar area is formed beforehand in the web, the position of cutting the lenticular lens 2 out of the web is decided. Thus, if some defective spots are found, the position of cutting-out cannot be shifted, thus reducing yield.
Furthermore, the lenticular lens 2 and the liquid crystal display cell I must be stuck to each other with accuracy of, e.g.,xe2x80x9425 xcexcm in order to prevent an image quality problem. However, for the lenticular lens 2 itself, the accuracy of pitches for the condenser lens portions 7 is set equal toxe2x80x9420 xcexcm in the manufacturing process. Thus, for this sticking, alignment between the lenticular lens 2 and the liquid crystal display cell 1 must be performed with very high accuracy ofxe2x80x945 xcexcm.
The present invention was made with the foregoing technical problems in mind, and the object of the present invention is to provide a method of alignment between sheet materials, a method of alignment, a substrate assembling method, and an aligning apparatus, which are capable of easily and surely performing highly accurate alignment and suppressing a reduction in material yield.
In order to achieve the foregoing object, according to the present invention, a method of alignment between sheet materials comprises the steps of: setting a focus of a microscope on a first sheet material in the laminated state of first and second sheet materials to perform measurement for a position of a specified portion of the first sheet material, setting the focus of the microscope on the second sheet material to perform measurement for a position of a specified portion of the second sheet material; and performing alignment between the first and second sheet materials based on the measured positions of the first and second sheet materials.
By changing the focus of the microscope in the laminated state of the first and second sheet materials, the positions of the first and second sheet materials based on the microscope as a reference can be respectively understood.
In this case, the second sheet material may be transmissive or non-transmissive. However, brightness necessary for the position measurement at the microscope must be secured. Any order for the measurements of the specified portions of the first and second sheet materials can be employed.
If the second sheet material is a lens sheet having a plurality of lens portions arrayed side by side, the position of the lens sheet is measured at the joint of the lens portions adjacent to each other. The joint of the lens portions is sufficiently thin compared with a signal line or a gate line and, by performing alignment using this joint, highly accurate alignment can be realized.
If the first sheet material is a liquid crystal display cell including signal and gate lines and a black matrix disposed in a matrix shape, the position of the liquid crystal display cell can be measured based on the signal line, the gate line or the black matrix. In this case, the accuracy of alignment can be increased by measuring a position of a centerline in the width direction of the signal line, the gate line or the black matrix, and matching the centerline with the joint of the lens portions.
Further, by measuring the positions of the first and second sheet materials at a plurality of places, if the second sheet material is deviated with an angle from the first sheet material (deviated in a rotational direction), the quantity of the deviation can be measured, and alignment can be performed based on the measured quantity of the deviation.
According to the method of alignment of the present invention, a reference light is made incident on the glass substrate and the lens sheet laminated together from the lens sheet side, and the glass substrate is aligned relative to the reference light passed through the lens sheet. In this case, the reference light should preferably be parallel rays of light. In addition, the reference light should more preferably be condensed at the lens sheet, and projected as a band-like light to the glass substrate. If the reference light is made incident on the glass substrate from a direction roughly orthogonal to the same, the position of the reference light projected on the glass substrate can be easily specified.
Accordingly, since the reference light passed through the lens sheet forms an image on the glass substrate in the state of being condensed or dispersed by the lens sheet, the position of the image on the glass substrate is decided by the lens sheet. Thus, by aligning the glass substrate with the image of the reference light, the glass substrate can be aligned with the lens sheet.
For example, if the glass substrate is a liquid crystal display cell, the non-transmission portion of the glass substrate, such as the black matrix, the signal line and the gate line, can be aligned relative to the reference light.
According to the present invention, a method of alignment comprises: a first step of making parallel rays of light incident from a lenticular lens side in a laminated state of a liquid crystal display cell and the lenticular lens, and aligning the liquid crystal display cell relative to a band-like reference light obtained by condensing the parallel rays of light at one of the condenser lenses of the lenticular lens; a second step of performing measurement for a position of the wiring portion of the liquid crystal display cell by setting a focus of observing means on the liquid crystal display cell, and performing measurement for a joint of the condenser lenses by setting the focus of the observing means on the lenticular lens; and a third step of performing alignment between the liquid crystal display cell and the lenticular lens based on the measured positions of the wiring portion and the joint of the condenser lenses.
In the first step, deviation of the liquid crystal display cell in a rotational direction relative to the reference light may be corrected. In the third step, deviation between the lenticular lens and the liquid crystal display cell in a direction orthogonal to the extended direction of the condenser lens may be corrected.
In this case, a group of three pixels of R, G and B are arrayed in the liquid crystal cell. If one condenser lens of the lenticular lens is provided corresponding to the group of three pixels, alignment must be performed so as to prevent the condenser lens from being shifted by one or two pixels. In such a case, in the second step, the wiring portion such as a signal line corresponding to the group of three pixels can be specified by using a frame outside the display area of the liquid crystal display cell. Then, by performing measurement for the position of the specified wiring portion, the lenticular lens can be accurately aligned.
Alignment can also be performed between the liquid crystal display cell and the lenticular lens based on the centerline of the liquid crystal display cell as a reference by performing measurement for the positions of the wiring portion and the joint of the condenser lenses at two places spaced from each other with the centerline of the liquid crystal display cell held therebetween. Accordingly, compared with the case of alignment performed by using the end portion of the liquid crystal display cell as a reference, the effect of the manufacturing dimension error of the liquid crystal display cell or the lenticular lens can be limited. In this case, the centerline of the liquid crystal display cell means a line passing through the center of the surface (display area) of the liquid crystal displace cell like that shown in FIG. 1.
According to the present invention, a substrate assembling method comprises the steps of: laminating a glass substrate and a lens sheet by interpolating unhardened adhesive; performing measurement for positions of respective specified portions of the glass substrate and the lens sheet by changing a depth of focus at a microscope; performing alignment between the glass substrate and the lens sheet based on the result of the measurement; and hardening the adhesive.
Furthermore, according to the present invention, an aligning apparatus comprises: cell holding means; lens holding means; driving means for driving at least one of the cell and lens holding means; observing means capable of changing a depth of focus; position data obtaining means such as an image processor or the like for obtaining position data of the liquid crystal display cell and the lenticular lens based on an image obtained by the observing means; and control means for controlling the driving means based on the obtained position data. In addition, the aligning apparatus may further comprise a light source for emitting parallel rays of light to the lenticular lens.
The aligning apparatus further comprises: first observing means for measuring deviation between the liquid crystal display cell and the lenticular lens in a rotational direction; and second observing means for measuring deviation between the liquid crystal display cell and the lenticular lens in a direction orthogonal to a continuous direction of a lens portion. In addition, the second observing means can be disposed respectively in one and other end portions of the liquid crystal display cell.